In overhead projectors, and other similar large-format projection systems, lenses of considerable overall diameter are required. In order to keep expenditures within acceptable limits, simple lenses in the form of two meniscus elements are frequently used, with a mirror normally being provided between the two meniscus elements. The overall diameters of the meniscus elements can, for example, amount to 95 mm. The reproduction quality attainable using meniscus elements of this kind is, however, only of moderate order. Better overhead projectors, therefore, contain more expensive lenses, preferably three-element triplet-type anastigmatic systems, a deflecting mirror conveniently being arranged above the lens. Of course, the considerable extra costs incurred by the requisite lens sizes have to be accepted. These costs are due in particular to the quantity and quality of the optical glass needed.
It is an object of the invention to provide a projection lens which is highly suitable for overhead projectors and other similar applications, and which can be manufactured with comparatively little outlay and at low costs.